Analysis of Material Behaviour at High Strain Rates for Modeling Machining Processes

Today, in the field of numerical FEM simulation of processes, the availability of reliable material data and models is becoming more and more important. It is recognised that mechanical properties of materials are influenced by the conditions of loading. In all industrial forming processes the workpiece material is deformed at different rates of straining and at different temperatures: in the case of machining processes, the rate of straining in the shear zone is in the 10 3 -10 5 s -1 range. So a material constitutive model that does not take the effect of strain rates into account is not reliable. This work aims to present one approach to the problem of obtaining both data and a proper constitutive model of the material to be implemented into FEM code for the numerical simulation of machining processes. In this approach, material behaviour is studied at the wide range of temperatures and strain rates that are typical of machining processes. High strain rate tests cannot be done with conventional hydraulic machines, but the Split Hopkinson Pressure Bar offers an effective tool for studying the rate sensitivity of materials. A special heating device is utilised to raise the temperature of the specimen in order to analyse material behaviour at typical shearing zone and chip formation temperatures.